It is known that a chlorinated or chlorosulfonated polyolefin is produced by reacting a polyolefin dissolved or suspended in a solvent. It is also known that as this solvent, a halogenated compound is used such as carbon tetrachloride, chloroform, methylene chloride, and fluorobenzene.
The most proper solvent of these is carbon tetrachloride, which is employed in many industrial processes. However, use of carbon tetrachloride is not preferable in that the compound has recently come to be suspected as a substance which destroys ozone present in the stratosphere.
On the other hand, chloroform can also be used as the solvent to produce a chlorinated or chlorosulfonated polyolefin. However, the product is disadvantageously colored yellow and has problems in practical use, for example, that formulations containing the product are apt to undergo scorching.
Chlorinated polyolefins have excellent properties such as nonflammability, weatherability, ozone resistance, chemical resistance, and electrical characteristics, and because of this, they are used, for example, as a resin modifier for polyvinyl chloride and other polymers and in light-colored electric wires and light-colored sponges.
Chlorosulfonated polyolefins are being used in escalator handrails, LP gas hoses, light-colored electric wires, leisure boats, and others.
Because beauty in color is one of the characteristics of these applications, the discoloration of the chlorinated or chlorosulfonated polyolefins themselves can be said to be a fatal defect. Further, a short scorching time of formulations containing chlorinated or chlorosulfonated polyolefins, i.e., tendency for the formulations to be prone to scorching, results in impaired processing safety when the formulations are processed into final articles such as hoses and electric wires, etc. Therefore, the chlorinated or chlorosulfonated polyolefins obtained through reactions in the conventional chloroform solvent have been of low commercial value.
All chloroform products on the market, whether for industrial use or reagent grade, generally contain from 0.5 to 1.0% of ethyl alcohol as a stabilizer. The reason for this is that since chloroform is an unstable substance and readily generates harmful phosgene, ethyl alcohol is added to suppress the generation of phosgene. (See, for example, Iwanami Rikagaku Jiten (Dictionary of Physicochemistry), 3rd Edition, published by Iwanami Shoten)
In other words, the substance generally called chloroform always contains such an alcohol compound. However, in this invention, such chloroform containing an alcohol compound should be clearly distinguished from chloroform containing no alcohol compound. The alcohol compound as referred to herein means a compound having an -OH group, such as, for example, ethyl alcohol and methyl alcohol.
The present inventors previously found that chlorinated or chlorosulfonated polyolefins synthesized by using, as a solvent, chloroform from which an alcohol compound stabilizer has been removed are pure-white, are not colored, and have excellent scorching stability. In addition, there was no difference therebetween in strength, elongation, hardness, and other properties after vulcanization. That is, it was found that the pure-white products and the conventional discolored products obtained using alcohol-containing chloroform cannot be distinguished from each other when viewed from the standpoint of physical properties after vulcanization.
However, since the chloroform containing no stabilizer was so unstable, there was a possibility that virulently poisonous phosgene generates, for example, in a tank storing the chloroform, in a reactor where chlorination reaction or chlorination and chlorosulfonation reaction was conducted, and during drying, etc.
Under these circumstances, there has been a strong desire for a stabilizer which, when used with chloroform to synthesize chlorinated or chlorosulfonated polyolefins, does not cause products which are colored as in the chlorinated or chlorosulfonated polyolefins synthesized by using alcohol compound-containing chloroform as a solvent and does not cause formulations containing the synthesized products to undergo scorching, and which effectively suppresses generation of virulently poisonous phosgene during storage of the chloroform or chlorination reaction or chlorination and chlorosulfonation reaction.